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https://issues.apache.org/jira/browse/HBASE-30303?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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chaijunjie updated HBASE-30303:
-------------------------------
Description:
With RSGroup fallback enabled, a table may belong to an RSGroup that has no
online RegionServers. Its regions are therefore assigned to the default
RSGroup, or to any available RegionServer if the default group also has no
online servers.
The regions remain available on these fallback servers. However, *during every
balance run, RSGroupBasedLoadBalancer validates their current locations only
against the table’s original RSGroup.* *Because that group still has no online
RegionServers, all fallback-hosted regions are classified as misplaced. The
balancer then creates region move plans with no explicit destination, causing
the regions to be randomly reassigned among the fallback candidates*. The same
process repeats on every balance run, resulting in continuous and unnecessary
region movement even when the fallback servers are already balanced.
!screenshot-2.png!
was:
With RSGroup fallback enabled, a table may belong to an RSGroup that has no
online RegionServers. Its regions are therefore assigned to the default
RSGroup, or to any available RegionServer if the default group also has no
online servers.
The regions remain available on these fallback servers. However, *during every
balance run, RSGroupBasedLoadBalancer validates their current locations only
against the table’s original RSGroup.* *Because that group still has no online
RegionServers, all fallback-hosted regions are classified as misplaced. The
balancer then creates region move plans with no explicit destination, causing
the regions to be randomly reassigned among the fallback candidates*. The same
process repeats on every balance run, resulting in continuous and unnecessary
region movement even when the fallback servers are already balanced.
!screenshot-1.png!
> Regions can not balance when enable rsgroup fallback and all regionservers
> dead in one group
> --------------------------------------------------------------------------------------------
>
> Key: HBASE-30303
> URL: https://issues.apache.org/jira/browse/HBASE-30303
> Project: HBase
> Issue Type: Bug
> Components: Balancer
> Affects Versions: 2.6.6
> Reporter: chaijunjie
> Priority: Major
> Attachments: screenshot-2.png
>
>
> With RSGroup fallback enabled, a table may belong to an RSGroup that has no
> online RegionServers. Its regions are therefore assigned to the default
> RSGroup, or to any available RegionServer if the default group also has no
> online servers.
> The regions remain available on these fallback servers. However, *during
> every balance run, RSGroupBasedLoadBalancer validates their current locations
> only against the table’s original RSGroup.* *Because that group still has no
> online RegionServers, all fallback-hosted regions are classified as
> misplaced. The balancer then creates region move plans with no explicit
> destination, causing the regions to be randomly reassigned among the fallback
> candidates*. The same process repeats on every balance run, resulting in
> continuous and unnecessary region movement even when the fallback servers are
> already balanced.
> !screenshot-2.png!
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